[elm-discuss] Distinguishing HTTP error codes

[Michal Blazejczyk]

Hi all,

I'm just beginning to get into Elm, and I encountered an issue. My Elm app
is making a POST request (Http.post) and when the server returns 400 or
401, I get NetworkError instead of BadStatus which means that I cannot
distinguish between error codes.

Looking at Javascript generated by the Elm compiler, I see:

function toTask(request, maybeProgress)
{
// ...
xhr.addEventListener('error', function() {
callback(_elm_lang$core$Native_Scheduler.fail({ ctor: 'NetworkError'
}));
});
xhr.addEventListener('timeout', function() {
callback(_elm_lang$core$Native_Scheduler.fail({ ctor: 'Timeout' }));
});
xhr.addEventListener('load', function() {
callback(handleResponse(xhr, request.expect.responseToResult));
});
// ...
}


For 400 and 401 responses, the browser triggers the listener for 'error'.
Is there a way to have Elm generate a BadStatus in this case?

Best,
Michal

[Rafał Cieślak]

Did you look into Http.expectStringResponse
<http://package.elm-lang.org/packages/elm-lang/http/1.0.0/Http#expectStringResponse>?
I've never used it, but the docs say:

Maybe you want the whole Response: status code, headers, body, etc. This

lets you get all of that information. From there you can use functions like
Json.Decode.decodeString to interpret it as JSON or whatever else you want.

[Peter Damoc]

Are you able to confirm in the developer console or Postman or some other
tool that you are actually getting a 401 from the server?

I'm getting 400 and 401 just fine from my servers and Elm is encoding them
just fine as a BadStatus.



On Sun, Dec 3, 2017 at 5:36 AM, Michal Blazejczyk <

Post by Michal Blazejczyk
Hi all,
I'm just beginning to get into Elm, and I encountered an issue. My Elm
app is making a POST request (Http.post) and when the server returns 400 or
401, I get NetworkError instead of BadStatus which means that I cannot
distinguish between error codes.
function toTask(request, maybeProgress)
{
// ...
xhr.addEventListener('error', function() {
callback(_elm_lang$core$Native_Scheduler.fail({ ctor: 'NetworkError'
}));
});
xhr.addEventListener('timeout', function() {
callback(_elm_lang$core$Native_Scheduler.fail({ ctor: 'Timeout' }));
});
xhr.addEventListener('load', function() {
callback(handleResponse(xhr, request.expect.responseToResult));
});
// ...
}
For 400 and 401 responses, the browser triggers the listener for 'error'.
Is there a way to have Elm generate a BadStatus in this case?
Best,
Michal
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[Michal Blazejczyk]

Actually, this was a problem with CORS configuration on the server. Once I
fixed it, the problem in Elm went away.

Apologies and thank you :)

Best,
Michal

Post by Peter Damoc
Are you able to confirm in the developer console or Postman or some other
tool that you are actually getting a 401 from the server?
I'm getting 400 and 401 just fine from my servers and Elm is encoding them
just fine as a BadStatus.

Post by Michal Blazejczyk
Hi all,
I'm just beginning to get into Elm, and I encountered an issue. My Elm
app is making a POST request (Http.post) and when the server returns 400 or
401, I get NetworkError instead of BadStatus which means that I cannot
distinguish between error codes.
function toTask(request, maybeProgress)
{
// ...
xhr.addEventListener('error', function() {
callback(_elm_lang$core$Native_Scheduler.fail({ ctor: 'NetworkError'
}));
});
xhr.addEventListener('timeout', function() {
callback(_elm_lang$core$Native_Scheduler.fail({ ctor: 'Timeout' }));
});
xhr.addEventListener('load', function() {
callback(handleResponse(xhr, request.expect.responseToResult));
});
// ...
}
For 400 and 401 responses, the browser triggers the listener for
'error'. Is there a way to have Elm generate a BadStatus in this case?
Best,
Michal
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